Using the Xenon133 inhalation technique, the regional cerebral blood flow (rCBF) lab within the Clinical Brain Disorders Branch carries out investigations of rCBF (as an indicator of regional cortical metabolism) in a variety of neuropsychiatric patients and in normal subjects. Patients populations, including those with chronic schizophriena, affective disorder, obsessive-compulsive disorder, Huntington's disease, Parkinson's disease, Alzheimer's disease, and dyslexia are studied before and during various exploratory and therapeutic interventions. Normal control subjects matched for each patient study are investigated concurrently. Cortical metabolic concomitants of states of normal cognition and consciousness are also being explored. The Xenon133 method allows for multiple determinations of rCBF in a single individual who can thus serve as his or her own control while being studied serially under various cognitive and/or medication conditions. This allows paradigms to be designed to specifically test hypotheses about regional cortical function in disease states and normal higher cognitive function, and to specifically monitor experimental and therapeutic interventions in neuropsychiatric disorders. Careful and creative application of this versatile tool has produced important results. ExperiZ01MH02395 tailored to explore dorsolateral prefrontal cortex (DLPFC), an area of special interest in schizophrenia, have shown this area to be de-activated in patients with schizophrenia under conditions of cognitively specific, regionally selective demand upon this area -conditions under which normals increase metabolism in DLPFC. In contrast Huntington's disease patients, who are as cognitively impaired as schizophrenics, do not show DLPFC rCBF abnormality, but rather rCBF patterns similar to normal subjects. This is important evidence for the existence of subcortical dementia, which, until now, has been questioned by some.